It is known that a vehicle using run-flat tires can run ongoingly a certain distance at a comparatively high speed even if the tire goes flat because of puncture (referred to as “run-flat running”). Such a run-flat tire is provided with side reinforcing rubber having a substantial crescent cross-sectional shape to enhance bending rigidity of each sidewall portion. When the tire goes flat, the side reinforcing rubber suppresses vertical deflection of tire, hereby maintaining ongoing running.
However, the run-flat tire is more likely to increase in tire mass, so that it can lead to problems of deteriorations of fuel efficiency and ride comfort during normal running with tires at standard inflation pressure.
To solve the problems, the applicant of the present invention proposes a run-flat tire provided with recesses, which extended in the tire radial direction inwardly and outwardly and spaced in the tire circumferential direction, on an inner surface of a side reinforcing rubber (see the following Patent Document 1). The proposed run-flat tire could save the tire weight by reducing the volume of a side reinforcing rubber.
Patent Document 1: Japanese Patent Application Laid-Open No. 2005-67315.